In the meaning of the invention “oil-free housing” or “oil-free portion of a housing” means that in general no oil or hydraulic fluid is present in the housing or in the corresponding housing area or that the level of oil or the hydraulic fluid in the housing is located below the moving and rotating parts of the hydraulic machine. In this sense oil or hydraulic fluid-free however means that in this mentioned areas leakage fluid and/or lubrication oil is present and drops, if applicable, into a hydraulic fluid collecting area. Here, for such “dry” moving hydraulic machines the term Dry-Case machines was established by the relevant circle of experts in the art and will be used furthermore in the description of the invention.
Hydraulic machines of the Dry-Case-type of construction comprise the advantage over hydraulic machines, whose housings are filled with hydraulic fluid or oil, that loss of power can be avoided due to parts of the driving mechanism rotating and splashing in the oil. Further, air inclusion in the oil sump caused by the permanent stirring of the hydraulic fluid is avoided, whereby the overall necessary quantity of oil can be reduced. In Dry-Case hydraulic machines no partial quantities of hydraulic fluid, which are stirred foamy, are present and which “liquefaction” has to be waited for, before the hydraulic fluid can be provided air-free to a working circuit again. However, in dry-ruining Dry-Case hydraulic machines the problem of lubrication of the moving and rotating machine- and driving mechanism parts exists. For hydraulic machines, whose housings are filled with hydraulic fluid the former addressed problem of the lubrication of the parts movable relative to each other does not arise.
In DE 10 2009 048 099 B4 a Dry-Case hydraulic machine is described which is moving in an oil-free housing, whereby the lubrication of the moving machine parts is effected via leakage oil. Especially in machines, whose bearing positions of the driving shaft is spaced from the hydrostatic driving mechanism, it was seen that the lubrication of this bearings by leakage fluid is complicated and sometimes lubrication effected by leakage is not sufficient.
Therefore, it is an object of the invention to provide a simple and efficient possibility to supply to all machine parts of a hydraulic machine with an oil-free housing, which are being rotatable or movable relative to each other, with lubricant, whereby a reliable, robust and cost efficient supply with lubricant of the moving machine parts should be guaranteed.